Spark plug having a thermal primer ring



June 6, 1967 H. R. S CHNABEL SPARK PLUG HAVING A THERMAL PRIMER RING Filed Dec. 28, 1964 Harold RSchnabe] United States Patent 3,324,330 SPARK PLUG HAVING A THERMAL PRIMER RING Harold Robert Schnabel, 1917 SE. Reedway, Portland, Greg. 97202 Filed Dec. 28, 1964, Ser. No. 421,473 4 Claims. (Cl. 313-143) This invention relates to an improvement in spark plugs, and more particularly concerns a novel construction for a spark plug whereby a fuel mixture prior to being fired is primed by heating, to give generally better running operation of an internal combustion engine.

A general object of this invention is to provide a spark plug which includes means heated by the firing of a combustible mixture in the cylinder of an internal combustion engine that will retain its heat, and by so doing primes a succeeding fuel charge by preheating it prior to firing of the charge.

Another object is to provide such a spark plug including a thermal primer means that with the spark plug in opera tive position is situated well into the chamber in an engine which normally contains a charge while it is fired, thus to be in optimum position to be heated by the firing of such a charge.

In a preferred embodiment of the invention, a spark plug as contemplated includes a metallic ring which is heated by the firing of a charge, and which surrounds the electrodes in the spark plug where they come to close adjacency to form a spark gap.

A feature and object of this invention is to provide such a ring in a plug where the same is mounted on the plug through means inhibiting substantial loss of heat from the ring by conduction away from the ring. In this Way the ring tends to retain its heat, whereby it may best perform its priming function (by preheating a charge).

The thermal primer means, more specifically the ring indicated, is spaced axially beyond the threaded end of the spark plug casing, whereby gas circulation can take place around the ring. With this construction, and during repeated firings of the spark plug, blow off of combustion products is facilitated, and the spark plug tends to remain clean.

The foregoing objects and other features and advantages of the invention will become more fully apparent from a reading of the following description, which is to be taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side view in elevation of a spark plug according to one embodiment of the invention, with portions of the plug broken away at one end;

FIG. 2 is another side elevation of the spark plug, as the same would appear viewing it from the left in FIG. 1; and

FIG. 3 illustrates the base of the plug in FIGS. 1- and 2.

Bottoming the herein disclosed invention have been observations by the inventor that spark plugs known to him and of conventional construction have certain deficiencies resulting in fouling and other unreliable operation.

More specifically, and by way of example, with smaller internal combustion engine units such as are used in motorcycles, etc., carburetion may be relatively simple. it is not uncommon, for instance, to provide as carburetion for such an engine a pair of jets, comprising an idle jet for low speeds and a high-speed jet for high speeds. To eliminate the flat spot on the throttle as engine speeds are increased, the idle jet may have a relatively rich setting. While such an organization may be satisfactory where the motorcycle is operated over a variety of the usual road speeds, it has introduced problems with the usual spark plug when the motorcycle is 3 ,324,330 Patented June 6, 1967 ice operated for the most part only at idle or low speeds for an extended time. Under these circumstances, and because of the rich fuel setting necessary, there is incomplete combustion, and combustion products and residue build up in the plug thus to foul the plug and impair its firing characteristics. A motorcycle policeman, for instance, who has been assigned to parade duty or other activity where low speeds are prevalent often must change his plugs or else arrange to drive the motorcycle at high speeds for a time to take care of this fouling problem.

According to this invention, this fouling may be inhibited by providing thermal primer means in the plug which is heated by firing of a charge, and then primes by heating a succeeding charge utilizing the heat retained from the firing of the preceding charge. The primer means is constructed so that circulation therearound is permitted, and blow ofi is possible. The thermal primer means is positioned around the spark gap formed by the electrodes, well into the chamber where firing takes place. With the spark plug contemplated, more lean fuel mixtures may be used with a low-speed jet, for example, without impairing engine operation. With such lean mixtures, the plug may be operated with the engine idling for long periods without fouling occurring. Any tendency for an engine to run hot at high speeds may be compensated for by making the high-speed fuel mixture somewhat more rich. In this way, good running conditions may be maintained at all speeds, and fouling which ordinarily is a problem may be substantially eliminated.

Referring now to the drawings, the spark plug of the invention is indicated generally at 10. The plug includes the usual metal casing or shell 12, which at the base of the spark plug includes a hollow threaded end 14. Wtihin the casing, and protruding from the top of the casing, is an insulator 16 of electrical insulating material. The insulator surrounds an electrode 18 which terminates at its upper end in a portion 20 adapted to be connected to the usual hot conductor of an ignition system.

Threaded end 14 of the casing is threadably received within the usual plug opening for the cylinder of an internal combustion engine. Electrode 18 has a spark producing bottom end portion 22 which, in the embodiment of the invention illustrated, extends somewhat below the base of threaded end 14- of the casing.

Another electrode for the spark plug is shown at 24 which is mounted on and electrically joined to the casing, this electrode constituting the usual ground electrode. This electrode has an inturned outer end 26 which overlies and is adjacent spark producing end 22 of electrode 18, and which together with end 22 forms a spark gap for the plug. I

The plug contemplated further comprises a metal wire 28 (shown broken away in FIG. 1), which may be a bronze stainless steel alloy or other metal with characteristics that will withstand the usual heats produced within an engine cylinder. The wire includes a looped portion 30 which forms an annular ring of substantially but somewhat smaller diameter than the diameter of the base of the casing (see FIG. 2), said ring being spaced in an axial direction beyond the end of the casing. Because looped portion 30 has a somewhat smaller diameter than the diameter of the base of the casing, the plug may be screwed into a plug opening in the usual internal combustion engine with the looped portion passing freely through the plug opening. In a typical instance, the spacing of looped is common. The looped portion thus surrounds end 26 of the electrode where it forms a spark gap with electrode 18.

While the spacing between the two electrodes where the spark gap is defined may be about ,4 of an inch, loop portion 30 of the wire in the region it encircles the spark gap may be positioned approximately inch away from the spark gap, or a substantially greater distance than the spacing of the electrodes at the spark gap. This spacing is important, as it minimizes any tendency for the spark produced at the gap to be dissipated by having a spark result between the ring and electrode 18.

Looped portion 30 of the wire is supported in its position spaced from the end of the casing through post portion 32 which extends at right angles to the looped portion and into the casing at 34.

With the plug mounted in place in the plug opening of an internal combustion engine, the annular ring formed by looped portion 30 is positioned well into the combustion chamber for the cylinder and beyond the plug opening. This is best illustrated in FIGS. 1 and 2, where the dotted and dashed lines 25 designate the level of the top of the combustion chamber and bottom end of the plug opening receiving the plug with the plug installed in an internal combustion engine. The ring also is substantially around the region where ignition of a charge starts on firing, which is the location of the spark gap between the electrodes. When a charge is fired by a spark, looped portion 39 becomes hot through the heat produced by the combustion of the charge. The mounting for the ring is such as to inhibit heat loss by conduction away from the ring, there being a gap for the most part between the ring and the end of the casing, and post 32 providing a relatively small conductive path for heat away from the ring. As a consequence the ring remains at a high temperature for a short time, which is sufiicient to enable it to prime a succeeding charge by heating it. This renders the succeeding charge more easily ignited, which in turn enables the use of a more lean fuel mixture in the case of idle or low speed engine operation.

By reason of the spacing of the ring from the end of the casing, ga circulation is accommodated about all sides of the ring and in the region adjacent the spark gap 7 when a charge is ignited. This spacing accommodates blow off of combustion products, which inhibits any tendency for residue to collect on the ring and adjacent areas.

With the plug of the invention, and because of the thermal priming it produces, it has been found that more lean fuel mixtures may be used at low speeds, with more complete combustion of a charge and less tendencies for deposits to collect on the plug. This, together with the blow off feature mentioned, enables the plug to be used in applications where previously sustained operation at idle or near idle speeds produced spark plug fouling and faulty engine operation.

It is understood that while an embodiment of the invention has been described, variations and modifications are possible, and it is intended to cover all such variations and modifications of the invention as would be apparent to one skilled in the art and that come within the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. For an internal combustion engine having an engine wall with a plug opening extending through the engine wall communicating at one end with a combustion chamber, a spark plug comprising a shell having a hollow threaded end received within the plug opening, a first electrode mounted within said shell with an end portion encircled by said hollow threaded end of the shell, a second electrode joined to the shell with an end portion disposed outwardly from said end of said plug opening and adjacent said end portion of said first electrode to form a spark gap therewith, and thermal primer means adapted to be heated by the combustion of a fuel charge positioned out of contact with said engine wal and outwardly from the threaded end of said shell and outwardly from the end of said plug opening with a space thereby being defined which :permits the flow of gas between the said primer means and the end of said p opening, said thermal primer means being connected to the shell by means inhibiting heat conduction [from the thermal primer means to the shell, said thermal primer means being spaced from the said first electrode a distance greater than the distance separating the first and second electrodes at said spark gap.

2. For an internal combustion engine having an engine wall with a plug opening extending through the engine wall communicating at one end with a combustion chamber, a spark plug including a shell having a hollow threaded end received within the plug opening, a first electrode with a spark producing end adjacent the base of and surrounded by the threaded end of the shell, a second electrode joined to the shell with an end portion disposed outwardly from said end of said plug opening and spaced from said spark producing end of the first electrode to form a spark gap therewith, a metallic ring encircling said spark producing end of the first electrode out of contact with said engine wall and spaced axially from the threaded end of the shell and outwardly fr m the end of said plug opening whereby circulation of gas around the ring is accommodated, and a post mounting said ring on the threaded end of the shell, said ring being spaced radially from the two electrodes where they define said gap a distance substantially greater than the distance which forms the gap.

3. In a spark plug including a shell having a hollow threaded end adapted to be received within a plug opening for the cylinder of an internal combustion engine, said threaded end terminating in a plane substantially normal to the axis of the shell, a first electrode mounted within the shell having a spark producing end disposed at substantially the axial center of said hollow threaded end, a second electrode joined to the shell having an inturned end disposed adjacent but spaced from said spark producing end of the first electrode and forming with said spark producing end a spark gap, said inturned end lying in a plane substantially paralleling but spaced axially beyond the plane in which said threaded end terminates, a metallic ring of smaller diameter than the diameter of the threaded end of the shell spaced axially beyond the threaded end of the shell and substantially in the plane occupied by said inturned end of the second electrode and surrounding the spark gap defined by the first and second electrodes, and a post mounting said ring on said threaded end of the shell, said post supporting the rin in a position to be heated by charges ignited by the spark plug while accommodating insignificant escapement of heat from the ring by conduction from the ring through the post to the shell of the spark plug.

4. In a spark plug including a shell having a hollow threaded end adapted to be received within a plug opening for the cylinder of an internal combustion engine, said threaded end terminating in a plane substantially normal to the axis of the shell, a first electrode mounted within the shell having a spark producing end disposed at substantially the axial center of the hollow threaded end, a second electrode joined to the shell having an inturned end overlying said spark producing end of the first electrode, said inturned end lying in a plane which is spaced outwardly from the threaded end of the shell and which substantially parallels the plane in which said threaded end terminates, said inturned end Where it overlies said spark producing end of the first electrode defining a spark gap which is located inwardly toward the shell of the spark plug from said plane of the inturned end, a ring spaced outwardly from the threaded end of the shell substantially in the plane occupied by said inturned end of 5 6 the second electrode, and a post mounting said ring on References Cited said threaded end of the shell, said ring surrounding the UNITED STATES PATENTS spark gap defined by the first and second electrodes and 1 973 884 9/1934 Rabezzana 313 143 X said spark gap being located inwardly toward the end of 2:294:248 3/1942 Smulski 313 143 X the shell from said ring by reason of the ring occupying 5 substantially the plane of the inturned end of the sec- JAMES W. LAWRENCE, Primary Examiner. ond electrode. C. R. CAMPBELL, Assistant Examiner. 

1. FOR AN INTERNAL COMBUSTION ENGINE HAVING AN ENGINE WALL WITH A PLUG OPENING EXTENDING THROUGH THE ENGINE WALL COMMUNICATING AT ONE END WITH A COMBUSTION CHAMBER, A SPARK PLUG COMPRISING A SHELL HAVING A HOLLOW THREADED END RECEIVED WITHIN THE PLUG OPENING, A FIRST ELECTRODE MOUNTED WITHIN SAID SHELL WITH AN END PORTION ENCIRCLED BY SAID HOLLOW THREADED END OF THE SHELL, A SECOND ELECTRODE JOINED TO THE SHELL WITH AN END PORTION DISPOSED OUTWARDLY FROM SAID END OF SAID PLUG OPENING AND ADJACENT SAID END PORTION OF SAID FIRST ELECTRODE TO FORM A SPARK GAP THEREWITH, AND THERMAL PRIMER MEANS ADAPTED TO BE HEATED BY THE COMBUSTION OF A FUEL CHARGE POSITIONED OUT OF CONTACT WITH SAID ENGINE WALL, AND OUTWARDLY FROM THE THREADED END OF SAID SHELL AND OUTWARDLY FROM THE END OF SAID PLUG OPENING WITH A SPACE THEREBY BEING DEFINED WHICH PERMITS THE FLOW OF GAS BETWEEN THE SAID PRIMER MEANS AND THE END OF SAID PLUG OPENING, SAID THERMAL PRIMER MEANS BEING CONNECTED TO THE SHELL BY MEANS INHIBITING HEAT CONDUCTION FROM THE THERMAL PRIMER MEANS TO THE SHELL, SAID THERMAL PRIMER MEANS BEING SPACED FROM THE SAID FIRST ELECTRODE A DISTANCE GREATER THAN THE DISTANCE SEPARATING THE FIRST AND SECOND ELECTRODES AT SAID SPARK GAP. 